Integrated circuitry fabrication typically fabricates multiple discrete integrated circuits or chips over a single substrate. A typical substrate utilized today is a monocrystalline silicon wafer within and upon which integrated circuitry is fabricated. Regardless, at the completion of fabrication, the substrate is cut or otherwise processed to singulate the die into individual integrated circuitry chips/die. Typically, the individual chips/die are mounted and electrically connected with larger circuit boards, lead frames or other substrates which connect or otherwise become a part of some form of larger operable hardware.
In many applications, the individual die as connected/mounted to another substrate are encapsulated in epoxy resin mold materials for fixating and protecting the mounted chip. Typically, the epoxy mold compounds have a much higher thermal coefficient of expansion than that of the typical silicon die and even other substrate materials to which the die are mounted. These differences in thermal coefficients of expansion can result in considerable internal stresses in the ultimately encapsulated device, in some cases leading to circuitry failure.
One manner of overcoming the stress caused by differences in thermal coefficients of expansion includes silicon dioxide filler materials within the mold compound. Typically, the intent and effect is to modify the thermal coefficient of expansion of the pure molding material to better approximate that of the die and other substrate materials. Unfortunately, the hard silicon dioxide particles can create their own problems. Specifically, upon application and cure of the molding material, the silicon dioxide particles can penetrate into the outer passivation layers fabricated on the chip. This can result in the cracking of those layers as well as the material of the integrated circuitry underlying the passivation layers and lead to failure.
While the invention was motivated in addressing the above issues and improving upon the above-described drawbacks, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded (without interpretative or other limiting reference to the above background art description, remaining portions of the specification or the drawings) and in accordance with the doctrine of equivalents.